The rotational force of a motor may be used to drive a wide variety of devices. By way of example, the rotational force of motors may be used to drive the paper transport mechanisms of document scanners and printers, to drive the drive mechanisms of video and audio cassette tape recorders, or to provide the motive force for powering cars and ships.
In such applications, the speed at which the paper or tape is transported or at which the vehicle is moved may be controlled by switching the speed of rotation of the motors. Conventionally such rotational speed switchers are constituted by AC or DC servo motors which have built-in speed control capabilities, or by the provision of a gear-changing mechanism operated via a clutch.
Although use of an AC or DC servo motor provides full control over speed, such motors are expensive and are uneconomical and costly to use in applications requiring no more than perhaps two speed settings. Other problems are that AC servo motors are noisy and DC servo motors tend to be short lived. On the other hand, there are also drawbacks to conventional clutch and gear-changing arrangements, which tend to be complex and bulky and therefore increase the overall size of the apparatus in which they are used.
In view of the aforesaid drawbacks of the prior art arrangements, it is desirable to provide a quiet, low-cost two-speed rotational speed switcher which is long-lasting, compact and highly reliable.